Retain Statement

[need_sas_help]

Sorry, Actually my typing had some errors  and the new problem should as  below (there is some changes), can you please check it:

I have the following dataset with following variables:
ID (Character) test (character) date (character) result (numeric)


ID       test   date               result
101      run    15JUL1978           1
101      run    15JUL1978           2
101      run    15JUL1978           1
101      run    18JUL1976           1 
101      run    18JUL1976           1 
101      run    18JUL1976           1 
101      case   15OCT2014         5
101      case   15OCT2014         5
101      case   15DEC2017          .
102      rub     28MAR2017         7
102      rub     28MAR2017         6          
102      rub     29MAR                8
102      rub     APR2017             5

need retian statement used or proc sql to create a new variable "MAXRESULT" to 
retain the maxmimum value (by ID test  date(  meaning per time point) from the presvois itration and compare with the present one
and keep the maximum one and
NEED A RESULT Datset LIKE AS BELOW. Also need to pay attention to the incomplete date 
and missing result. 


ID       test   date               result    MAXRESULT
101      run    15JUL1978           1          1
101      run    15JUL1978           2          2
101      run    15JUL1978           1          2 
101      run    18JUL1976           1          1
101      run    18JUL1976           1          1 
101      run    18JUL1976           1          1
101      case   15OCT2014          5          5 
101      case   15OCT2014          5          5
101      case   15DEC2017           .          .
102      rub     28MAR2017         7           7 
102      rub     28MAR2017         6           7
102      rub     29MAR                8           8
102      rub     APR2017             5           5      


Thank you so much from the bottom of my heart.

[novinosrin]

data have;
input  (ID            test      date) (:$10.)                  result;
datalines;
101      run    15JUL1978           1
101      run    15JUL1978           2
101      run    15JUL1978           1
101      run    18JUL1976           1 
101      run    18JUL1976           1 
101      run    18JUL1976           1 
101      case   15OCT2014         5
101      case   15OCT2014         5
101      case   15DEC2017          .
102      rub     28MAR2017         7
102      rub     28MAR2017         6          
102      rub     29MAR                8
102      rub     APR2017             5
;

data want;
set have;  
by id date notsorted;
retain 	max_result;
if first.date then call missing(max_result);
max_result=ifn(missing(result), ., max(max_result,result));
run;